Unhelpful error if an executable cannot be run
If the Python executable to be used for a part cannot be run (perhaps because its path has a typo or whatever), the attempt to find out its version number takes the OS's error message for the command output and raises an exception when trying to interpret the string as "Python x.y.z":
An internal error occured due to a bug in either zc.buildout or in a
recipe being used:
Traceback (most recent call last):
installed_files = self[part]
eggs, ws = self.egg.
pystring, version = version.split()
ValueError: too many values to unpack
The error message should say that the executable cannot be run, and display the path used in the attempt.